The two young girls found dead in a Weld County oil tank were strangled, court documents filed Friday by their father’s defense attorneys suggest.

The girls’ father, Christopher Watts, was arrested Wednesday in connection to the deaths of the girls, who were 3 and 4, and their mother, Shanann Watts. Christopher Watts’ defense attorney requested Friday that the girls’ necks be swabbed for DNA evidence “in spite of the fact that the remains were in oil for four days,” according to court documents posted by Denver7.

“I have a lot of experience taking samples from dead bodies getting good results after strangulation,” a DNA expert, Richard Eikelenboom, wrote in his recommendation to the defense attorneys.

The expert also recommended taking samples from the girls’ hands as well as from the nails and hands of the girls’ mother, whose body was found near the oil tank. The expert did not recommend and the defense attorney did not request a DNA sample from the mother’s neck.

“In my opinion the presence of oil will not destroy the DNA,” Eikelenboom said, according to the defense’s motion asking that the specific DNA samples be taken.

A Weld County District judge denied the requests.

A Denver District Court judge did not allow Eikelenboom to testify as an expert witness in a 2016 sexual assault trial after he admitted that he had no direct experience in DNA extraction or analysis, that his lab was unaccredited, that he failed his proficiency tests in 2011 and 2012, and that he trained himself to run DNA profiles.

Police arrested Christopher Watts, 33, late Wednesday night in connection with the death of his wife and two daughters, 4-year-old Bella and 3-year-old Celeste. He is being held in Weld County Jail without bail on suspicion of three counts of first-degree murder and three counts of tampering with evidence.

The Weld County Coroner’s Office completed autopsies on the three bodies Friday and confirmed that they were those of the mother and the girls.

The Weld County District Attorney’s Office is expected to file formal charges against Watts by 3:30 p.m. Monday. The charges will be read at Watts’ next court hearing, at 10 a.m. Tuesday.

At the request of prosecutors, a judge sealed the affidavit explaining why police believe he is a suspect in the death of his family. Weld County District Attorney Michael Rourke said Thursday that he expected the judge to unseal the affidavit Monday.

Watts was being held in protective custody because of the publicity the case has received, Denver7 reported Friday.

Law enforcement and prosecutors have refused to answer some questions about the case, citing an ongoing investigation.

What we don’t know yet:

How Shanann Watts was killed

What time the mother and her daughters were killed

The exact location of where their bodies were found

The formal charges to be filed against Christopher Watts

What the motive was for the killings

A family friend reported Monday afternoon that she hadn’t heard from Shanann. Police responded at 1:40 p.m. to the Watts home in the 2800 block of Saratoga Trail to check on the family, but did not find Shanann or her daughters.

SafeHouse Denver: safe-house-denver.org. Reach local professionals by calling the 24-hour crisis and information line at 303-318-9989.

Law enforcement canvassed the neighborhood, a small suburban development outside Frederick, for the next two days. The Colorado Bureau of Investigation declared Shanann and the two girls “endangered missing” on Tuesday.

Late Wednesday night, investigators arrested Christopher Watts in connection with the deaths. He appeared in court Thursday for a bond hearing, where prosecutors said the three victims were killed in the house on Saratoga Trail.

By Thursday evening, all three bodies had been recovered from an Anadarko property where they were left.

Elise Schmelzer is a breaking news reporter at The Denver Post. She previously wrote for the Casper Star-Tribune in Wyoming, the Washington Post and the Colorado Springs Gazette. When she's not writing, she disappears into the mountains to hike and fish.

More in Crime & Courts

A former University of Colorado employee is suing the school for wrongful termination, alleging he was passed over for teaching opportunities because of his race and then fired when he finally was given a teaching job as retribution for reporting the alleged discrimination.